indices

Calc Software Package for Number Calc

NAME
    indices - indices for specified matrix or association element

SYNOPSIS
    indices(V, index)

TYPES
    V		matrix or association
    index	integer

    return	list with up to 4 elements

DESCRIPTION
    For 0 <= index < size(V), indices(V, index) returns list(i_0, i_1, ...)
    for which V[i_0, i_1, ...] is the same lvalue as V[[index]].

    For other values of index, a null value is returned.

    This function can be useful for determining those elements for which
    the indices satisfy some condition.	 This is particularly so for
    associations since these have no simple relation between the
    double-bracket index and the single-bracket indices, which may be
    non-integer numbers or strings or other types of value.  The
    information provided by indices() is often required after the use
    of search() or rsearch() which, when successful, return the
    double-bracket index of the item found.

EXAMPLE
    ; mat M[2,3,1:5]

    ; indices(M, 11)
    list (3 elements, 2 nonzero):
	    [[0]] = 0
	    [[1]] = 2
	    [[2]] = 2

    ; A = assoc();

    ; A["cat", "dog"] = "fight";
    ; A[2,3,5,7] = "primes";
    ; A["square", 3] = 9

    ; indices(A, search(A, "primes"))
    list (4 elements, 4 nonzero):
	    [[0]] = 2
	    [[1]] = 3
	    [[2]] = 5
	    [[3]] = 7

LIMITS
    abs(index) < 2^31

LINK LIBRARY
    LIST* associndices(ASSOC *ap, long index)
    LIST* matindices(MATRIX *mp, long index)

SEE ALSO
    assoc, mat

## Copyright (C) 1999-2006  Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
## as published by the Free Software Foundation.
##
## Calc is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
## or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU Lesser General
## Public License for more details.
##
## A copy of version 2.1 of the GNU Lesser General Public License is
## distributed with calc under the filename COPYING-LGPL.  You should have
## received a copy with calc; if not, write to Free Software Foundation, Inc.
## 59 Temple Place, Suite 330, Boston, MA  02111-1307, USA.
##
## @(#) $Revision: 29.3 $
## @(#) $Id: indices,v 29.3 2006/06/10 12:28:10 chongo Exp $
## @(#) $Source: /usr/local/src/cmd/calc/help/RCS/indices,v $
##
## Under source code control:	1999/11/16 08:02:03
## File existed as early as:	1999
##
## chongo <was here> /\oo/\	http://www.isthe.com/chongo/
## Share and enjoy!  :-)	http://www.isthe.com/chongo/tech/comp/calc/